/* ----------------------------------------------------------------------
* Copyright (C) 2010 ARM Limited. All rights reserved.
*
* $Date:        15. February 2012
* $Revision: 	V1.1.0
*
* Project: 	    CMSIS DSP Library
* Title:	    arm_fir_lattice_q15.c
*
* Description:	Q15 FIR lattice filter processing function.
*
* Target Processor: Cortex-M4/Cortex-M3/Cortex-M0
*
* Version 1.1.0 2012/02/15
*    Updated with more optimizations, bug fixes and minor API changes.
*
* Version 1.0.10 2011/7/15
*    Big Endian support added and Merged M0 and M3/M4 Source code.
*
* Version 1.0.3 2010/11/29
*    Re-organized the CMSIS folders and updated documentation.
*
* Version 1.0.2 2010/11/11
*    Documentation updated.
*
* Version 1.0.1 2010/10/05
*    Production release and review comments incorporated.
*
* Version 1.0.0 2010/09/20
*    Production release and review comments incorporated
*
* Version 0.0.7  2010/06/10
*    Misra-C changes done
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup FIR_Lattice
 * @{
 */


/**
 * @brief Processing function for the Q15 FIR lattice filter.
 * @param[in]  *S        points to an instance of the Q15 FIR lattice structure.
 * @param[in]  *pSrc     points to the block of input data.
 * @param[out] *pDst     points to the block of output data
 * @param[in]  blockSize number of samples to process.
 * @return none.
 */

void arm_fir_lattice_q15(
    const arm_fir_lattice_instance_q15* S,
    q15_t* pSrc,
    q15_t* pDst,
    uint32_t blockSize)
{
	q15_t* pState;                                 /* State pointer */
	q15_t* pCoeffs = S->pCoeffs;                   /* Coefficient pointer */
	q15_t* px;                                     /* temporary state pointer */
	q15_t* pk;                                     /* temporary coefficient pointer */


#ifndef ARM_MATH_CM0

	/* Run the below code for Cortex-M4 and Cortex-M3 */

	q31_t fcurnt1, fnext1, gcurnt1 = 0, gnext1;    /* temporary variables for first sample in loop unrolling */
	q31_t fcurnt2, fnext2, gnext2;                 /* temporary variables for second sample in loop unrolling */
	q31_t fcurnt3, fnext3, gnext3;                 /* temporary variables for third sample in loop unrolling */
	q31_t fcurnt4, fnext4, gnext4;                 /* temporary variables for fourth sample in loop unrolling */
	uint32_t numStages = S->numStages;             /* Number of stages in the filter */
	uint32_t blkCnt, stageCnt;                     /* temporary variables for counts */

	pState = &S->pState[0];

	blkCnt = blockSize >> 2u;

	/* First part of the processing with loop unrolling.  Compute 4 outputs at a time.
	 ** a second loop below computes the remaining 1 to 3 samples. */
	while(blkCnt > 0u) {

		/* Read two samples from input buffer */
		/* f0(n) = x(n) */
		fcurnt1 = *pSrc++;
		fcurnt2 = *pSrc++;

		/* Initialize coeff pointer */
		pk = (pCoeffs);

		/* Initialize state pointer */
		px = pState;

		/* Read g0(n-1) from state */
		gcurnt1 = *px;

		/* Process first sample for first tap */
		/* f1(n) = f0(n) +  K1 * g0(n-1) */
		fnext1 = (q31_t)((gcurnt1 * (*pk)) >> 15u) + fcurnt1;
		fnext1 = __SSAT(fnext1, 16);

		/* g1(n) = f0(n) * K1  +  g0(n-1) */
		gnext1 = (q31_t)((fcurnt1 * (*pk)) >> 15u) + gcurnt1;
		gnext1 = __SSAT(gnext1, 16);

		/* Process second sample for first tap */
		/* for sample 2 processing */
		fnext2 = (q31_t)((fcurnt1 * (*pk)) >> 15u) + fcurnt2;
		fnext2 = __SSAT(fnext2, 16);

		gnext2 = (q31_t)((fcurnt2 * (*pk)) >> 15u) + fcurnt1;
		gnext2 = __SSAT(gnext2, 16);


		/* Read next two samples from input buffer */
		/* f0(n+2) = x(n+2) */
		fcurnt3 = *pSrc++;
		fcurnt4 = *pSrc++;

		/* Copy only last input samples into the state buffer
		   which is used for next four samples processing */
		*px++ = (q15_t) fcurnt4;

		/* Process third sample for first tap */
		fnext3 = (q31_t)((fcurnt2 * (*pk)) >> 15u) + fcurnt3;
		fnext3 = __SSAT(fnext3, 16);
		gnext3 = (q31_t)((fcurnt3 * (*pk)) >> 15u) + fcurnt2;
		gnext3 = __SSAT(gnext3, 16);

		/* Process fourth sample for first tap */
		fnext4 = (q31_t)((fcurnt3 * (*pk)) >> 15u) + fcurnt4;
		fnext4 = __SSAT(fnext4, 16);
		gnext4 = (q31_t)((fcurnt4 * (*pk++)) >> 15u) + fcurnt3;
		gnext4 = __SSAT(gnext4, 16);

		/* Update of f values for next coefficient set processing */
		fcurnt1 = fnext1;
		fcurnt2 = fnext2;
		fcurnt3 = fnext3;
		fcurnt4 = fnext4;


		/* Loop unrolling.  Process 4 taps at a time . */
		stageCnt = (numStages - 1u) >> 2;


		/* Loop over the number of taps.  Unroll by a factor of 4.
		 ** Repeat until we've computed numStages-3 coefficients. */

		/* Process 2nd, 3rd, 4th and 5th taps ... here */
		while(stageCnt > 0u) {
			/* Read g1(n-1), g3(n-1) .... from state */
			gcurnt1 = *px;

			/* save g1(n) in state buffer */
			*px++ = (q15_t) gnext4;

			/* Process first sample for 2nd, 6th .. tap */
			/* Sample processing for K2, K6.... */
			/* f1(n) = f0(n) +  K1 * g0(n-1) */
			fnext1 = (q31_t)((gcurnt1 * (*pk)) >> 15u) + fcurnt1;
			fnext1 = __SSAT(fnext1, 16);


			/* Process second sample for 2nd, 6th .. tap */
			/* for sample 2 processing */
			fnext2 = (q31_t)((gnext1 * (*pk)) >> 15u) + fcurnt2;
			fnext2 = __SSAT(fnext2, 16);
			/* Process third sample for 2nd, 6th .. tap */
			fnext3 = (q31_t)((gnext2 * (*pk)) >> 15u) + fcurnt3;
			fnext3 = __SSAT(fnext3, 16);
			/* Process fourth sample for 2nd, 6th .. tap */
			/* fnext4 = fcurnt4 + (*pk) * gnext3; */
			fnext4 = (q31_t)((gnext3 * (*pk)) >> 15u) + fcurnt4;
			fnext4 = __SSAT(fnext4, 16);

			/* g1(n) = f0(n) * K1  +  g0(n-1) */
			/* Calculation of state values for next stage */
			gnext4 = (q31_t)((fcurnt4 * (*pk)) >> 15u) + gnext3;
			gnext4 = __SSAT(gnext4, 16);
			gnext3 = (q31_t)((fcurnt3 * (*pk)) >> 15u) + gnext2;
			gnext3 = __SSAT(gnext3, 16);

			gnext2 = (q31_t)((fcurnt2 * (*pk)) >> 15u) + gnext1;
			gnext2 = __SSAT(gnext2, 16);

			gnext1 = (q31_t)((fcurnt1 * (*pk++)) >> 15u) + gcurnt1;
			gnext1 = __SSAT(gnext1, 16);


			/* Read g2(n-1), g4(n-1) .... from state */
			gcurnt1 = *px;

			/* save g1(n) in state buffer */
			*px++ = (q15_t) gnext4;

			/* Sample processing for K3, K7.... */
			/* Process first sample for 3rd, 7th .. tap */
			/* f3(n) = f2(n) +  K3 * g2(n-1) */
			fcurnt1 = (q31_t)((gcurnt1 * (*pk)) >> 15u) + fnext1;
			fcurnt1 = __SSAT(fcurnt1, 16);

			/* Process second sample for 3rd, 7th .. tap */
			fcurnt2 = (q31_t)((gnext1 * (*pk)) >> 15u) + fnext2;
			fcurnt2 = __SSAT(fcurnt2, 16);

			/* Process third sample for 3rd, 7th .. tap */
			fcurnt3 = (q31_t)((gnext2 * (*pk)) >> 15u) + fnext3;
			fcurnt3 = __SSAT(fcurnt3, 16);

			/* Process fourth sample for 3rd, 7th .. tap */
			fcurnt4 = (q31_t)((gnext3 * (*pk)) >> 15u) + fnext4;
			fcurnt4 = __SSAT(fcurnt4, 16);

			/* Calculation of state values for next stage */
			/* g3(n) = f2(n) * K3  +  g2(n-1) */
			gnext4 = (q31_t)((fnext4 * (*pk)) >> 15u) + gnext3;
			gnext4 = __SSAT(gnext4, 16);

			gnext3 = (q31_t)((fnext3 * (*pk)) >> 15u) + gnext2;
			gnext3 = __SSAT(gnext3, 16);

			gnext2 = (q31_t)((fnext2 * (*pk)) >> 15u) + gnext1;
			gnext2 = __SSAT(gnext2, 16);

			gnext1 = (q31_t)((fnext1 * (*pk++)) >> 15u) + gcurnt1;
			gnext1 = __SSAT(gnext1, 16);

			/* Read g1(n-1), g3(n-1) .... from state */
			gcurnt1 = *px;

			/* save g1(n) in state buffer */
			*px++ = (q15_t) gnext4;

			/* Sample processing for K4, K8.... */
			/* Process first sample for 4th, 8th .. tap */
			/* f4(n) = f3(n) +  K4 * g3(n-1) */
			fnext1 = (q31_t)((gcurnt1 * (*pk)) >> 15u) + fcurnt1;
			fnext1 = __SSAT(fnext1, 16);

			/* Process second sample for 4th, 8th .. tap */
			/* for sample 2 processing */
			fnext2 = (q31_t)((gnext1 * (*pk)) >> 15u) + fcurnt2;
			fnext2 = __SSAT(fnext2, 16);

			/* Process third sample for 4th, 8th .. tap */
			fnext3 = (q31_t)((gnext2 * (*pk)) >> 15u) + fcurnt3;
			fnext3 = __SSAT(fnext3, 16);

			/* Process fourth sample for 4th, 8th .. tap */
			fnext4 = (q31_t)((gnext3 * (*pk)) >> 15u) + fcurnt4;
			fnext4 = __SSAT(fnext4, 16);

			/* g4(n) = f3(n) * K4  +  g3(n-1) */
			/* Calculation of state values for next stage */
			gnext4 = (q31_t)((fcurnt4 * (*pk)) >> 15u) + gnext3;
			gnext4 = __SSAT(gnext4, 16);

			gnext3 = (q31_t)((fcurnt3 * (*pk)) >> 15u) + gnext2;
			gnext3 = __SSAT(gnext3, 16);

			gnext2 = (q31_t)((fcurnt2 * (*pk)) >> 15u) + gnext1;
			gnext2 = __SSAT(gnext2, 16);
			gnext1 = (q31_t)((fcurnt1 * (*pk++)) >> 15u) + gcurnt1;
			gnext1 = __SSAT(gnext1, 16);


			/* Read g2(n-1), g4(n-1) .... from state */
			gcurnt1 = *px;

			/* save g4(n) in state buffer */
			*px++ = (q15_t) gnext4;

			/* Sample processing for K5, K9.... */
			/* Process first sample for 5th, 9th .. tap */
			/* f5(n) = f4(n) +  K5 * g4(n-1) */
			fcurnt1 = (q31_t)((gcurnt1 * (*pk)) >> 15u) + fnext1;
			fcurnt1 = __SSAT(fcurnt1, 16);

			/* Process second sample for 5th, 9th .. tap */
			fcurnt2 = (q31_t)((gnext1 * (*pk)) >> 15u) + fnext2;
			fcurnt2 = __SSAT(fcurnt2, 16);

			/* Process third sample for 5th, 9th .. tap */
			fcurnt3 = (q31_t)((gnext2 * (*pk)) >> 15u) + fnext3;
			fcurnt3 = __SSAT(fcurnt3, 16);

			/* Process fourth sample for 5th, 9th .. tap */
			fcurnt4 = (q31_t)((gnext3 * (*pk)) >> 15u) + fnext4;
			fcurnt4 = __SSAT(fcurnt4, 16);

			/* Calculation of state values for next stage */
			/* g5(n) = f4(n) * K5  +  g4(n-1) */
			gnext4 = (q31_t)((fnext4 * (*pk)) >> 15u) + gnext3;
			gnext4 = __SSAT(gnext4, 16);
			gnext3 = (q31_t)((fnext3 * (*pk)) >> 15u) + gnext2;
			gnext3 = __SSAT(gnext3, 16);
			gnext2 = (q31_t)((fnext2 * (*pk)) >> 15u) + gnext1;
			gnext2 = __SSAT(gnext2, 16);
			gnext1 = (q31_t)((fnext1 * (*pk++)) >> 15u) + gcurnt1;
			gnext1 = __SSAT(gnext1, 16);

			stageCnt--;
		}

		/* If the (filter length -1) is not a multiple of 4, compute the remaining filter taps */
		stageCnt = (numStages - 1u) % 0x4u;

		while(stageCnt > 0u) {
			gcurnt1 = *px;

			/* save g value in state buffer */
			*px++ = (q15_t) gnext4;

			/* Process four samples for last three taps here */
			fnext1 = (q31_t)((gcurnt1 * (*pk)) >> 15u) + fcurnt1;
			fnext1 = __SSAT(fnext1, 16);
			fnext2 = (q31_t)((gnext1 * (*pk)) >> 15u) + fcurnt2;
			fnext2 = __SSAT(fnext2, 16);

			fnext3 = (q31_t)((gnext2 * (*pk)) >> 15u) + fcurnt3;
			fnext3 = __SSAT(fnext3, 16);

			fnext4 = (q31_t)((gnext3 * (*pk)) >> 15u) + fcurnt4;
			fnext4 = __SSAT(fnext4, 16);

			/* g1(n) = f0(n) * K1  +  g0(n-1) */
			gnext4 = (q31_t)((fcurnt4 * (*pk)) >> 15u) + gnext3;
			gnext4 = __SSAT(gnext4, 16);
			gnext3 = (q31_t)((fcurnt3 * (*pk)) >> 15u) + gnext2;
			gnext3 = __SSAT(gnext3, 16);
			gnext2 = (q31_t)((fcurnt2 * (*pk)) >> 15u) + gnext1;
			gnext2 = __SSAT(gnext2, 16);
			gnext1 = (q31_t)((fcurnt1 * (*pk++)) >> 15u) + gcurnt1;
			gnext1 = __SSAT(gnext1, 16);

			/* Update of f values for next coefficient set processing */
			fcurnt1 = fnext1;
			fcurnt2 = fnext2;
			fcurnt3 = fnext3;
			fcurnt4 = fnext4;

			stageCnt--;

		}

		/* The results in the 4 accumulators, store in the destination buffer. */
		/* y(n) = fN(n) */

#ifndef  ARM_MATH_BIG_ENDIAN

		*__SIMD32(pDst)++ = __PKHBT(fcurnt1, fcurnt2, 16);
		*__SIMD32(pDst)++ = __PKHBT(fcurnt3, fcurnt4, 16);

#else

		*__SIMD32(pDst)++ = __PKHBT(fcurnt2, fcurnt1, 16);
		*__SIMD32(pDst)++ = __PKHBT(fcurnt4, fcurnt3, 16);

#endif /*      #ifndef  ARM_MATH_BIG_ENDIAN    */

		blkCnt--;
	}

	/* If the blockSize is not a multiple of 4, compute any remaining output samples here.
	 ** No loop unrolling is used. */
	blkCnt = blockSize % 0x4u;

	while(blkCnt > 0u) {
		/* f0(n) = x(n) */
		fcurnt1 = *pSrc++;

		/* Initialize coeff pointer */
		pk = (pCoeffs);

		/* Initialize state pointer */
		px = pState;

		/* read g2(n) from state buffer */
		gcurnt1 = *px;

		/* for sample 1 processing */
		/* f1(n) = f0(n) +  K1 * g0(n-1) */
		fnext1 = (((q31_t) gcurnt1 * (*pk)) >> 15u) + fcurnt1;
		fnext1 = __SSAT(fnext1, 16);


		/* g1(n) = f0(n) * K1  +  g0(n-1) */
		gnext1 = (((q31_t) fcurnt1 * (*pk++)) >> 15u) + gcurnt1;
		gnext1 = __SSAT(gnext1, 16);

		/* save g1(n) in state buffer */
		*px++ = (q15_t) fcurnt1;

		/* f1(n) is saved in fcurnt1
		   for next stage processing */
		fcurnt1 = fnext1;

		stageCnt = (numStages - 1u);

		/* stage loop */
		while(stageCnt > 0u) {
			/* read g2(n) from state buffer */
			gcurnt1 = *px;

			/* save g1(n) in state buffer */
			*px++ = (q15_t) gnext1;

			/* Sample processing for K2, K3.... */
			/* f2(n) = f1(n) +  K2 * g1(n-1) */
			fnext1 = (((q31_t) gcurnt1 * (*pk)) >> 15u) + fcurnt1;
			fnext1 = __SSAT(fnext1, 16);

			/* g2(n) = f1(n) * K2  +  g1(n-1) */
			gnext1 = (((q31_t) fcurnt1 * (*pk++)) >> 15u) + gcurnt1;
			gnext1 = __SSAT(gnext1, 16);


			/* f1(n) is saved in fcurnt1
			   for next stage processing */
			fcurnt1 = fnext1;

			stageCnt--;

		}

		/* y(n) = fN(n) */
		*pDst++ = __SSAT(fcurnt1, 16);


		blkCnt--;

	}

#else

	/* Run the below code for Cortex-M0 */

	q31_t fcurnt, fnext, gcurnt, gnext;            /* temporary variables */
	uint32_t numStages = S->numStages;             /* Length of the filter */
	uint32_t blkCnt, stageCnt;                     /* temporary variables for counts */

	pState = &S->pState[0];

	blkCnt = blockSize;

	while(blkCnt > 0u) {
		/* f0(n) = x(n) */
		fcurnt = *pSrc++;

		/* Initialize coeff pointer */
		pk = (pCoeffs);

		/* Initialize state pointer */
		px = pState;

		/* read g0(n-1) from state buffer */
		gcurnt = *px;

		/* for sample 1 processing */
		/* f1(n) = f0(n) +  K1 * g0(n-1) */
		fnext = ((gcurnt * (*pk)) >> 15u) + fcurnt;
		fnext = __SSAT(fnext, 16);


		/* g1(n) = f0(n) * K1  +  g0(n-1) */
		gnext = ((fcurnt * (*pk++)) >> 15u) + gcurnt;
		gnext = __SSAT(gnext, 16);

		/* save f0(n) in state buffer */
		*px++ = (q15_t) fcurnt;

		/* f1(n) is saved in fcurnt
		   for next stage processing */
		fcurnt = fnext;

		stageCnt = (numStages - 1u);

		/* stage loop */
		while(stageCnt > 0u) {
			/* read g1(n-1) from state buffer */
			gcurnt = *px;

			/* save g0(n-1) in state buffer */
			*px++ = (q15_t) gnext;

			/* Sample processing for K2, K3.... */
			/* f2(n) = f1(n) +  K2 * g1(n-1) */
			fnext = ((gcurnt * (*pk)) >> 15u) + fcurnt;
			fnext = __SSAT(fnext, 16);

			/* g2(n) = f1(n) * K2  +  g1(n-1) */
			gnext = ((fcurnt * (*pk++)) >> 15u) + gcurnt;
			gnext = __SSAT(gnext, 16);


			/* f1(n) is saved in fcurnt
			   for next stage processing */
			fcurnt = fnext;

			stageCnt--;

		}

		/* y(n) = fN(n) */
		*pDst++ = __SSAT(fcurnt, 16);


		blkCnt--;

	}

#endif /*   #ifndef ARM_MATH_CM0 */

}

/**
 * @} end of FIR_Lattice group
 */
